Related Articles

Tree mushrooms, especially those in the form of conks or bracts that do not have stems, also called shelf mushrooms, can cause wood to rot. The decay is typically found on the interior of the tree and so you cannot see it. There are no chemicals or fungicides that can eradicate tree mushrooms. The best measure is to prevent their appearance by proper care and by cutting away infected wood.

Tree Mushroom Damage

Mushrooms causing white rot break down the cellulose and lignin in wood, making it appear white or yellow and soft, moist, spongy or stringy. Lignin seals the space between walls of cellulose cells that form xylem, vessels that transport water and nutrients in a tree. Mushrooms causing brown rot are more serious. Brown rot, sometimes called dry rot, causes wood to become dry and crumbly. Soft rot grows more slowly and usually only damages wood close to the fungi and does not cause serious damage to a tree.

White Rot Mushrooms

Mycologists at the University of California-Davis, have identified a number of mushrooms that cause white rot in fruit and landscape trees. Oak root fungus (Armillaria mellea) grows leafy mushrooms at the base of trees. Artist’s conk (Gandoderma), a shelf mushroom that is brown on top and white on the bottom, causes white rot on numerous landscape trees. The bright red conks of varnish fungus rot (Ganoderma lucidum) can kill a wide variety of fruit trees in three to five years. The familiar, edible oyster mushroom (Pleurotus ostreatus) causes white rot. The grayish-white common split gill mushroom (Schizophyllum commune) produces white rot in some 75 species of landscape trees. The turkey tail mushroom (Trimetes versicolor) that has concentric stripes and the hairy turkey tail (Trimetes hirsute) are shelf mushrooms that cause brown rot.

Brown Rot Mushrooms

The 2- to 12-inch-wide conks of the sulfur fungus (Laetiporus sulphureus) are moist, soft and fleshy when they are young; they turn hard and brittle as they get older. They are orange-yellow on top and red yellow on their undersides when they are young and white when they mature. They cause serious decay of oak and yew trees.

Managing Tree Mushrooms

Tree mushrooms typically cause wood decay on large, mature trees. Protect trees from injury that often lead to the development of mushrooms. Prune dead or diseased limbs. If you prune young trees so that they develop a good form, you do not have to remove a large limb from an older tree. When you do prune a large branch, make your cut just outside of the bark roll that develops where the branch grows from the trunk. Leave a collar of growing tissue around the cuts so the wound can heal itself. Do not leave a stub. Trees respond to conks by forming natural chemical barriers. Do not use commercial wound paints when you prune; as these age, they can crack, trapping water inside and increasing the risk of tree mushrooms growing on the wound.